APPLICATIONS OF
PHOTOVOLTAIC CELL
INTRODUCTION
Photovoltaic power generation is
a method of producing electricity using
solar cells. A solar cell converts solar
optical energy directly into electrical
energy. A solar cell essential a
semiconductor device fabricated in a
manner which generates a voltage when
solar radiation falls on it and it converts
into electrical energy by the chemical
reaction.
 1839 - French physicist A. E. Becquerel first recognized the photovoltaic effect.
 1883 - first solar cell built, by Charles Fritts, coated semiconductor selenium with
an extremely thin layer of gold to form the junctions.
 1954 - Bell Laboratories, experimenting with semiconductors, accidentally found
that silicon doped with certain impurities was very sensitive to light. Daryl Chapin,
Calvin Fuller and Gerald Pearson, invented the first practical device for converting
sunlight into useful electrical power. Resulted in the production of the first practical
solar cells with a sunlight energy conversion efficiency of around 6%.
 1958 - First spacecraft to use solar panels was US satellite Vanguard 1
PHOTO VOLTAIC CELL
 The most common type of solar cells are
Photovoltaic Cells (PV cells).
 Converts sunlight directly into electricity.
 Cells are made of a semiconductor material (eg.
silicon).
 Light strikes the PV cell, and a certain portion is
absorbed.
 The light energy (in the form of photons) knocks
electrons loose, allowing them to flow freely, forming a
current.
 Metal contacts on the top and bottom of PV cell
draws off the current to use externally as power.
MATERIALS USING IN IT
▪ Pure silicon is a poor conductor of
electricity.
▪ “Doping” of silicon with phosphorus
and boron is necessary to create n-type
and p-type regions.
▪ This allows presence of free electrons
and electron-free ‘holes’.
▪ The p-n junction generates an electric
field that acts as a diode, pushing
electrons to flow from the P side to the
N side.
Material using for PV cells:
•silicon (Si),
•gallium arsenide (GaAs),
•cadmium telluride (CdTe),
•copper indium diselenide (CIS),
PV TECHNOLOGY CLASSIFICATION
Silicon Crystalline
Technology
Thin Film
Technology
Mono Crystalline
PV Cells
Amorphous Silicon
PV Cells
Multi Crystalline
PV Cells
Poly Crystalline PV
Cells
SILICON CRYSTALLINE TECHNOLOGY


Currently makes up 86% of PV market
Very stable with module efficiencies 10-16%
Mono crystalline PV Cells
Multi Crystalline PV Cells
•Made
using saw-cut from single
cylindrical crystal of Si
•Caste
•Operating
•Cell
efficiency up to 15%
from ingot of melted
and recrystallised silicon
efficiency ~12%
•Accounts
for 90% of
crystalline Si market
THIN FILM TECHNOLOGY
Silicon deposited in a continuous on a
base material such as glass, metal or
polymers

Thin-film crystalline solar cell consists
of layers about 10μm thick compared
with 200-300μm layers for crystalline
silicon cells

AMORPHOUS SILICON PV CELLS
The most advanced of thin film
technologies

POLY CRYSTALLINE PV CELLS
Copper Indium Diselinide:

Operating efficiency ~6%
CIS with band gap 1V, high absorption
coefficient 105cm-1

Makes up about 13% of PV market


High efficiency levels
CONVERTING LIGHT INTO ELECTRICITY
 Photons reach emitter layer.
 Energy releases electrons from
silicon.
 Electrons (-) are attracted to base
region (+).
- -  Holes (+) in the base are- - then
attracted to emitter region.
 This is a flow of electricity.
 Electricity will flow through the two
contacts.
 Same principle as a diode.
n-type Silicon
- - - - - - + + + + + + + + + + + +
p-type Silicon
 Various factors effect power o/p from panels.
 Shade or Clouds.
 Panel position or angle.
 Active panels can track the sun.
 Temperature and solar irradiance variations.
 Air gap required for cooling.
 Partial shading will reduce performance and
can cause damage.
Power (W)
 Fig. shows the I-V curve and power o/p of a solar
panel.
 If no load is connected with solar panel, an open
circuit voltage Voc will produced but no current
follows.
 If the terminals of the solar panel are shorted
together, the short-circuit current Isc will flow but the
output voltage is zero.
 In both cases no power is delivered by the PV cell.
 When a load is connected, we need to consider the
V-I curve of the load to figure out how much power can
be delivered to the load.
 The maximum power point(MRP) is the spot near
the knee of the V-I curve.
Current (A)
CHARACTERISTICS OF PV CELL
Voltage (V)
Fig shows equivalent circuit of a solar cell. The diode current Id = Io (e^(Avd) - 1) comes from the standard V-I
equation for a diode. It is clear that the current I that flows to the external circuit is,
I=Isc – Io(e^(Avd) – 1)
Where,
Isc = short circuit current.
Io = reverse saturation current of the diode.
A = temperature dependent constant
Photovoltaic effect
When a solar cell (p-n junction) is
illuminated, electron-hole pairs are generated
and the electric current obtained I is the
difference between the solar light generated
current IL and the diode dark current Ij, i.e,
I = IL - I j
I = IL - IO[exp ( eV / kT ) - 1]
This phenomenon is known as the photovoltaic effect
EFFICIENCY OF SOLAR CELLS
 The amount of power available from a PV device is
determined by,
 Type and area of the material
 The intensity of the sunlight
 The wavelength of the sunlight
 Single crystalline solar cells  25% efficency
 Polycrystalline silicon solar cells  less than 20%
 Amorphous silicon solar cells  less than 10%
 Cells are connected in series to form a panel to
provide larger voltages and an increased current
PV CELLS & COMPONENTS
The Photovoltaic System Includes:
 Arrays
 Optional Batteries
 Battery Controller
 Inverter
 Mounting Systems
ARRAYS AND SYSTEMS
 Panels of solar cells can be linked together to form a larger system – an array
a)
b)
c)
d)
e)
f)
g)
A PV panel array, ranging from two to many hundreds of panels.
A control panel, to regulate the power from the panels.
A power storage system, generally comprising of a number of
specially designed batteries.
An inverter, for converting the DC to AC power (eg 240 V AC).
Backup power supplies such as diesel startup generators (optional).
Framework and housing for the system.
Trackers and sensors (optional).
 Lead acid batteries are used to store PV-generated
electricity.
 A battery is an electrochemical cell. The electric
potential between the positive and negative electrodes is
about 2 volts direct current (DC).
 The battery can off-gas oxygen from the positive
electrode and hydrogen from the negative electrode.
 Escaping gases are highly flammable, sparks and open
flames are not allowed near the batteries.
 Like the PV modules, batteries are wired in series and
parallel to provide the voltage and amperage necessary for
the operation of the electrical system
 To keep battery charge levels in check, a
charge controller is used in the PV system.
 The battery charge controller prevents over
charging reducing the danger of off-gassing.
 Many controllers also protect the battery
from over-discharges as well.
 Battery charge controllers are found in offgrid systems and grid-tied systems that have a
battery back-up.
 PV modules can be mounted directly on the
roof, in many cases specialized roof racks lift the
array from the roof deck allowing air to circulate
under the modules.
 Many PV systems are designed to withstand 80
mile per hour winds.
 PV systems can also be mounted on the ground
using customized racks, or they can be mounted on
poles.
• Toys, watches, calculators
• Electric fences
• Remote lighting systems
• Water pumping
• Water treatment
• Emergency power
• Portable power supplies
• Satellites
 Another farm application – keeping animals
where they belong, behind PV-electrified fence
chargers.
 The lamp in this PV-powered
insect-trap
comes
on
automatically after sunset. It
attracts insects which collide
with the metal grid and drop
into the receiver below.
 In
1987,
the
Swiss
government started a program
to mount PV arrays on a sound
barrier
along
a
main
motorway.
 Maybe no uses are as dramatic and
important as the portable PV panels and
small refrigerators carried around Africa
on the backs of camels.
 Highway directional signs can use
systems to save the expense
excavation to extend electric lights
the sign as well as the cost
maintaining the electric line.
PV
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to
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